Technology update

Apr 25, 2005

Platinum nanoparticles bring spontaneous ignition

Researchers at Oak Ridge National Laboratory, US, have found that platinum nanoparticles can cause a mixture of methanol and air to ignite spontaneously at room temperature. The combustion reaction was able to proceed at just a few tenths of a degree above room temperature.

“Since caveman days, we have burned things to use their energy, and the high temperatures and the entire process have created a lot of problems that we’re then forced to deal with,” said Zhiyu (Jerry) Hu of Oak Ridge. “What we have is the possibility of retrieving energy at a lower temperature with greater efficiency and lower environmental effects.”

Catalysis normally requires preheating, a process that can prove very expensive in industrial applications. Hu believes that his low-temperature catalysis findings could reduce operational costs, minimize system complexity and improve reaction efficiency.

Hu discovered the effect by accident while conducting another experiment. He supported platinum nanoparticles between 50 and 700 nm in size on 10 µm-diameter quartz glass fibres in a quartz reaction tube. Flowing methanol/air or ethanol/air mixtures through the tube caused spontaneous ignition to take place.

The scientists were able to alter the pace of the reaction by adjusting the fuel/air ratio, gas flow-rate and nanoparticle size and morphology. Depending on the conditions, the reaction took place at temperatures between just a few tenths of a degree above room temperature and more than 600°C. The reaction products were water and carbon dioxide.

Using bulk platinum in place of platinum nanoparticles did not produce the same reaction. And nanoparticles with a diameter of around 100 nm were more active than particles bigger than 500 nm across. The activity of the nanoparticles also decreased at high humidity.

Hu says that the reaction mimics nature since organisms obtain energy by oxidizing organic chemicals at their body temperature. Many of these reactions also use metals as part of their enzyme catalysts.